Pilot operated fuel control valve for gas turbines



Aug. 14, 1956 H. T. MARCY ErAL 2,758,812

PILOT OPERATED FUEL CONTROL VALVE FOR GAS TURBINES Original Filed J'an. 5, 1951 I9 Arm/wn l United States Patent O PILOT OPERATED FUEL CONTROL VALVE FOR"` GAS TURBINES Henry-Tyler Marcy, Vestal, N. Y., and Robert. James Fylfe; Perth Amboy, N. 3.,. assignors to The M. W. Kellogg Company, Jersey City, N. J., a corporation of Delaware Originali application'n January 5, 1951, Serial- No.. 204,634'. Divided` and this application November 4, 1954; Serial No. 466,913

This invention relates in general to fluid flowcontrol systems and' in particular to aV control valve for a system" for controlling the temperature of the gases issuing from' a gas generator. This application is a division of. our application Serial No. 204,634, filed January S, 1'951.

Ithas been proposed in connection With liquid propel lant rocket motors, to drive the gas turbine ofthe turbopump set thereof by means of a stream of hot gases produced in a separate gas generator by the interaction of the components of the uid propellant used by the motor; To successfully carry out this proposal it is necessary that. the hot gases reach the turbine at temperatures low enough. for safe turbine operation and yet high enough and constantenough for etlicienty and steady turbineperformance.

The liquid rocket propellants used at presentcomprise a. fuel, component and an oxidizing component, The reactionbetween the components of the liquidfrockeLpro-f pellant. israpid, tends to progress rapidly to .completion and liberates large quantities of energy. They interaction-.of these, components in stoichiometric proportions results in gaseous reaction products at temperatures greatly in excess of the temperatures that can safely be withstoodb-y the gas turbine.. By changing. the mixture ratio. of the. components in` either direction fromv the stoichiometric ratio, the temperature of thegaseous.y reactionprod-uets may be reduced'to valuesy suliciently low for safe gasturbine operation. The safe temperature range. is. limitedI as it is. not possible to vary the=mixture ratio too greatly from the.l stoiehiome-tric ratio without entering a range in which the reaction becomes erratic andy undependable. The reaction temperature-mixture ratioy curve of the'components is generally quite steep; hence', small variations in mixture ratio produce large temperature variations. Because of these characterisf tics of the components of the liquid propellants andvof their reaction, the attainment of a satisfactory gasy sup'- ply for the:gas. turbine by controlling the mixturefratio ofthe components supplied to the gas. generator presents a problem which cannot be: solved in a simple and; prac tical manner.

It is. the, principal object of the invention toprovide al simple, practical control valve for a system for supply'- inga steady stream of hot gases within. a predetermined tempera-ture range to a gas turbine of: ay rocketl motor by reactingvthe components of the liquid propellant used by the rocket motor, which does not depend'on'the accurate cont-rol. ot' the mixture ratio of the components.

.It is a further.' principal object of the invention to1prov-ideacontrol, valve fora systemof thefcharacter-mcnk ti'onedffory supplying a steady stream of hot gases, Within a; predetermined temperature range, to a gastunbine'by reactingl the. components of'. the liquid rocket. propellant in,- a 'gast generator chamber at. a chosen: mixtureratio suchfA as to. proviclewhot gaseous. reaction=products ati tlre upper end@ ofzor above. said. predetermined; temperature abovef 1500 safely.

Patented Aug. 14, 1956 ICC for changes in temperatureA of the hot gaseous reaction products due tov extraneous causes, and supplying to said chamber one or the other of said components. at controlle'd. rates to cool said gaseous products to vmaintain them within said predetermined temperature range.

lt is also a principal object of therinvention to provide a simple and' compact valving arrangement for said hot gas supply .systemwhich is sensitive to small variations intemperature of the hot gases leaviugthe gas generator and which is capable of elfecting Wide and rapidvariations in the rate of supply of the component used as the cooling medium in the gas generator.

The further objects', features and' advantages. of the invention willbe apparent from the following detailed description of theinvention taken with the accompanying drawings, in which:.

Fig. l is a diagrammatic view of the gas generating system of the invention; and

Fig.. 2.i`s.. a longitudinal sectional view off the controlk mechanism usedin .said system.r

While theinvention isof. general application and may advantageously be.4 used in variousy arts4 where temperature and flow control are of importance, itwill be. disclosed vinty connection with. liquid propellant*v rocketv motorsand in particular inr connectionwith asystem forz supply,-r ing hot gases to the turbine employed todrivez-the pumps which pressurize the components o-fthe liquidA propellanty on their way' to the motor chamber ofvtherocket.

LiquidV propellantsused for rocket motors include: a fuel. component, for example gasoline, and-an oxidizer component, for example fuming nitricacid. Thesercomponents' react rapidly to produce: highlyy heated gaseous products. When gasoline and fuming nitric` acid:` are reacted in stoicliiometric. proportions the reactiony productstattain temperatures inexcess of 45.00 E. By varying the proportions of the components in. either direction from ther stoichiometric ratio the1 temperature'v of'4 the reactionfproducts may be rapidly andi materially reduced. Smallr variations in the ratio of' the` components. result in largen variationsy in the temperature' of' the. reaction products,

While it isidesirable from an eiiiciencyI standpoint'to operate gas turbinesat'high temperatures,because/ofthe limitations imposed by the m'aterialsfoutofI which the turbines are constructed, it is not possible' to" go much In order toV maintain turbine eliciencies within satisfactory limits, gas' temperatures below 1300.-" F. are avoided; Also, itis highly'desirabl'e that?:gasV temperature' variations-be kept toV a minimum;

The novel system 10 of this invention, shown ini'Fig; 1, oters-r a= simple and reliable solution to the problem. The lsystem-includes a gas generator 1I into which open the valvedliquid propellant component supplyV linesy 12 and The oxidizer component is' preferably supplied through thelineV 12 While the`y fuel component is preferably supplied" through the line 1f3; The-lines 12VA and 13 arepreferably'directly connected to the'mai-n'pumps,- not shown; of the roclzetV motor. The' gas generator charnber 1*1 includes an ignition device', not shown, such as' the conventional glow plug, and' an injector arrangement, also not shown, of conventional form. If the injector device includesmetering orifices thel valves inv lines 12 and 1% may be omitted. The hotl gaseous combustion products pass from the' generator 11 through a'VA conduit 114 to the .inletv manifold' of the gas turbine Projecting intothe conduitr14' is a: tl'nermostatic` device 16,- tot be more particularly described hereinafter, which includes a pivotedllever 17 that` operates.- the control device 18g also to" be4 described' in detail hereinafter.. A: line 19 .connects the. control device. l8r.- to the line liwhilea line 20 connects the control device 1S to the gas generator 11. A line 21 connects the control device 18 to a sump, not shown.

In operation the Valves in lines 12 and 13 are initially adjusted to give the mixture ratio that will provide a predetermined reaction temperature. This predetermined reaction temperature will be at least 1500 F., but preferably higher. For better operation and better temperat-ure control, it has been found desirable to employ reaction temperatures greatly in excess of l500 F., temperatures produced by reacting the components in the stoichiometric ratio or in ratios approaching the stoichiometric ratio having been employed with satisfactory results'. The thermostatic device 16 and the control device 18 are set to maintain a predetermined gas temperature at the manifold 15. This predetermined operating temperature will depend on the closeness of the control that the control device 18 exercises. Thus, if device 18 permits variations as great as 100 F., a predetermined temperature of 1400 F. will be satisfactory; if the maximum variation is only 50 F. then 1450 F. can safely be chosen.

The thermostatic device 16 acts upon the control device 18 and their joint :action is such that when the temperature of the gaseous reaction products passing through the conduit 14 exceeds or tends to exceed the predetermined operating temperature, the component from line 13 will pass through the lines 19 and 20 and be injected into the gas generator chamber 111 at controlled rates to reestablish said operating temperature. The injected component evaporates and gasiiies in the chamber 11 and thus cools the gaseous reaction products. Since in the preferred mode of operation the reaction temperature of the components supplied through lines 12 and 13 is always chosen at or above the upper end of Xthe safe operating range, 15001300 F., #there will always be injection into the chamber 11 of the componeut from the lines 19 and 20. The variation in rate of injection will be comparatively small, as it will only be necessitated by variations in the reaction temperature due to extraneous causes.

While it is also possible to operate the system by choosing reaction temperatures that approximate the operating temperatures, such operation does not lend itself to close control as the ow of the injected component is intermittent and there is no control if the reaction temperature should fall below the operating temperature.

Referring now to Fig. 2, wherein are shown control arrangements having the simplicity, positiveness and sensitivity necessary for the successful operation of the system just described: The thermostatic device 16 includes a tube 22 having a closed lower end and formed of a material of as high a coeilcient of expansion as possible that will successfully resist exposure to the gaseous products owing through the conduit 14. The upper end of the tube 22 is expanded against and welded to 'the walls of the central bore in the gland member 23 which is screw-threaded into the central bore of the lateral extension 24 of the conduit 14. A gasket 25, fitting in a recess in extension 24 is interposed between said extension and the extending flange of the gland 23 to seal the joint between them. The central bore of the gland 23 is enlarged for the major portion of its length to accommodate a coil spring 26 and a washer 27. A cap 28 screws onto the upper end of the gland 23 and abuts the upper end of the spring 26. The washer 27 has a central two diameter bore. The larger, lower portion of this bore accommodates the upper end of the rod 29. The spring 26 through the washer 27 constantly urges the rod 29 into contact with the closed end of the tube 22. The rod 29 is made of a material of minimum, or zero, coeicient of expansion. The upper end of the rod 29 is recessed and accommodates the end of rod 30 that passes through the smaller upper portion of the central bore of the washer 27. The upper end of the rod 30 is bifurcated and mounts a pin 31 passing through a slotted hole in the lever 17 to permit pivoted movement of the rod 30 about said lever. The end of the lever 17, adjacent the pin 31, is positioned between the tines of the bifurcated support member 32. The tines of member 32 and said end of the lever 17 are each provided with a multiplicity of spaced holes 33, only three being shown, adapted to receive the pin 34 which mounts the lever 17 for pivotal movement. By moving the pin 34 from one to another set of holes 33 the ratio of movement of lever 17 and rod 30 may be varied. The support member 32 is fastened as by cap screws 35 to the bracket 36 which in turn is fastened by the cap screws 37 to the ange of the extension 24. The other end of the lever 17 carries a screw 38 passing therethrough which serves as an adjustable contact member and is locked in adjusted position by the set screw 39.

The tubular valve body 40 is attached to the lower end of the bracket 36, as by means of the studs and nuts 41, and is provided with the tapped bores 42 and 43 that receive the usual attachment nipples, not shown, for connection to the ends of the lines 19 and 20 respectively. The bottom end of the body 40 is closed while the top end is open and threaded to receive the gland 44. A seal ring 45 seals the joint between the gland 44 and the body 40. The upper portion 46 of the central bore of the body 40 is of larger diameter than the lower portion 47, a shoulder is thus provided upon which rests the flange 49 of the sleeve member 50. Spaced peripheral portions of the flange 49 are cut away, to provide a plurality of passageways 511, only one being shown, opening into the bore 46 above the flange 49 and into the bore 47 below said flange. The lower end of the sleeve 50 is in the form of a flangelike extension l52 whose outer peripheral surface contacts the walls defining the bore 47. The flange 52 includes a groove housing the seal ring 53. The central bore 54 of the sleeve 52 is enlarged adjacent its lower end to dene in part the annular chamber 55. A plurality of bores 56 open into the chamber S5 and in-to that section of bore 47 between the flanges 49 and 52.

The upper end of the sleeve 50 contacts a snap ring 57 carried in a recess formed in the tubular cap 58 which is screwed into the gland 44. The snap ring 57 holds the sleeve 50 in position in the central bore of the body member 40. The cap 58 is locked in position by a nut S9 threaded thereon and adapted t-o bear on the top of the gland 44. A seal ring 60 is positioned between the cap 58, the nut 59 and the gland 44 and prevents leakage.

The stem 61 of the spool 62 extends into the lower end of the central bore 54 of the sleeve 50. integral with the stem 61 is a hollow piston 63. A spring 64 is housed in the hollow of the piston 63 and urges said piston upwardly to seat the conical valve surface 65, 'formed adjacent the lower end of the stem 61 against the shoulder 66 at the lower end of the bore 54. Above said surface 65 the stem 61 is recessed to define in part the chamber 55. A metering passageway 67 is formed in the lower end of the stem 61 opening in to the central hollow of said stem and into the lower portion of the bore 47.

The tubular cap has press 'fitted into the upper end thereof a sleeve member 70. The bore sections 71, '72, '73 and 74 make up the central bore of the sleeve 70 and house a valve stem member 75. The sleeve member 70 has a longitudinal peripheral groove 76 cut therein which intersects the radial groove 77 cut in the top surface thereof. The grooves 76 and 77 provide a passageway opening into the upper end of the bore section 71 and into the lower end of the central bore of the cap member 58. The cap member 58 includes a threaded bore 79 which receives the nipple 80 to which is connected the end of the sump line 21. The sleeve 70 at the level of the bore 79 has a portion of its wall cut away, Aas by a milling cutter, to provide a passageway 81 opening into the bore section 72 and into the threaded bore 79.

The valve stem'l member 7Slincludes an enlargedA piston portion 82 having al peripheral. groove inlwliichditsfthe seal ring 83. At the lower end-of the Valve stem member 75is a second enlarged piston portion madeup of the sections 84 and 85. Between the sections 84 and 85is a groove 86. The lower end of the piston section 85 retains the-spring 87 whose bottomjend rests on the castellated upperI end of thesleeve 88. The spring 87 urges the valve stem 75- upwardlyl toseat thesection-85 on the shoulderat the junctionY of the bore sections 74 and 73. rFhe'flower end of the sleeve 8S isl anged to tit loosely in the'lower end' of' thecentral bore of the cap'mernb'er 58 andrest'on the-snap ring 57'.' Thevalve'stern'75. includes a rod 'member'89 which extends from-the upper endof the pistonA enlargement SZand is adapted to be contacted screw 38'. The rod 892'is encircled for a substantial portion of its length4 bythe deformable bushing seal. 90' which i's pressed into an appropriately shaped recess in the threaded extension 91 of 'thecap SSby a metal retainer 92; The retainer is removed downwardly by a capv 93 threaded on the extension 91.A

The pistonenlargement S2" andthe piston enlargement section 84 are of such diameter that while leakage past them is a minimum, ,they may be moved alongthe respective bore sections v71 and 73 with a minimum-of resistance. Also, the areas of piston sections 82`and85" and thegroove 36 aresuch and areso disposed that the .force producedby the pressure of the fuel component thereon. tending t0 move the valve stem 75 upwardly is substantially balanced by the force produced by the pressure of, the. fuellcomponent on the surface of the upper end of the piston enlargement 82 tending to move the valveA stem.75A downf wardly. Thus, the lever 17 need overcome essentially only'the force exerted by the spring.8.7 and theffrctional resistances ofseals 83 and 90 in movingrthe valve: stem 75downwardly, and as, the lever 17 movesupwardly, the springy 87 need only overcome the weight ofthe valve stem 75 and the.- frictionalfresistances of the seals.- 83- and 90 to, raise said valve stem witht-he lever 17.l

I'n order thatthe device 18 be sensitive, to small temperature differences. and provide for rapidadjustments due` to-large. temperature differences, it is necessary that the. valve: stem 75. in the initial phases of. its downward movement from the position of Fig. 2 permit only.V small flow from the bore sec-tion 74 to bore section721andthat in. later phases of saiddownward movement pennitmuch greater tlow. To this end, the valve stem. 75 has;V an arcuate groove 95. cut therein. The groove 95A has; a V-shaped cross-section and ispreferably cut by a; milling cutter. The bottom end. ofthe groove 95-is-slightly above thev groove. 86- and is separated therefrom by a: narrow ledge. The. depth of the groove 9S increasesl from-.its lower end in a non-linear manner for a distance-,substanttially: equal to the maximum downward. movement of. the valvezstem member 7S.

Assuming that the screw 38- has been lock-ed in ad# .justedzfpositio-n such thatI the lower.- end, ofthe groove-95 willbe. moved past the shoulder between the.bo-ref sections 72 and 74 the amount required to maintain the temperature of the; hot gases i=nthe" conduit`14- at- 114903 F., the lines l2 and 13,-are atv-.full pump:pressure;l 60G-800 p. s. i., that ignition has been started but that ther gaseousreaction products in the conduit 1'4 have not attainedltemperatures approach-ing the safe operating range, 130041500 F., and that the components are supplied in such proportion that the gaseous reaction products attain a temperature ot` the order of 2500 F. The elements of the devices 16 and 18 will be positioned as in Fig. 2. The static pressure around the spool 62 will be the same as the static pressure within the spool 62 so that the valve surface 65 will be maintained in contact with the shoulder 66 through the pressure exerted by the spring 64 since the spool 62 is constructed to be completely pressure-balanced under these conditions. The same static pressure will also attain in bore section 74 and at the top of the bore section 71" so-thar the section-SS'oi thevalvestem 'TS will"y alsoebe; held aga-inst its` seat solelythrough the pressure of the spring-87.

As the temperature in the conduit increases the tube 22 will lengthen'and springZtiA will mover0d-29` downwardly. The rod- 30'-will follow the rodZSlito-rotateL lever 1=7fabout the pin'34 and'ultimatelfy the-'screw 38fwillfm'ovethe valve stem` 75 downwardly to carry the; lower end'of'the groove 951past the shoulder between'the bore sections 72 and74. When this occurs the component' fromthe line 19 will flow from the bore section 74-intolthe bore-section andthence throughy line 21 to the sump; This flow will causel a'ow of the same value through thepassageway 6T andthrougl'i. the hollow ofthe spool- 62 with the result that the static pressure'v within the spool will?v be reduced. As the expansion of' tube 22 continues, the static pressure difference between the outsidel andthe inside of the spool will ultimately beenough to-'overcome the force exertedby the-springv64`and the spool wilflmove downwardly to'unseat the surface 65' and' How will" talee place into-chamber 55 and thence through bore 46-and the-line20 into the gas generator `chamber 11 whereinthe injected component will be evaporated and gasifed and thuscoolitl'ie'gaseous reaction-products. The downward movement of the valve stern 75`fandtthe resultant increase in flow through line 20 will continuev until the temperature of the gases iny the cond-uit14- reaches the predetermined temperatureof"y 1400'o F. if' the reaction conditions do not chan-ge there will be no'further` change in the rate-of liow into' the line 205 However, ifv for anyg'reason the reaction conditionschange-'and the temperature ofv the gasesvvi-n-conduit 114 tends to:I increase,` the further eX-pan sion ofthe tube-22 will result in a further increase inthe rateot` flowinto the line 20. lf, however, the change in reactiony conditions-tends toY reduce the temperature ofthe gases in conduit I4, the'tube 22 willV contract and thet following vmovement of the rod 29` Wil-l raise Vthe lever 117. The-spring 87v willI move the Valve stem'89to'fo1'low the` contact 38 and'v theflow through the'groove 95 will ber diminished. The reduc-tion inow will'increase the static'pressure within tlre'spoolI 62# so that the spring- 63 willlmove'the spoolf 6-2y upwards Itoreduce the iiow' into the chamber' SSf-thus yreduc-ingY the rate of flow through the line 20.

Although manyv changes can be made byqthose skilled in the'art without departingfromthescope'of the invention, it isl'i-ntended that all matterl contained-in the above description and appendedclaims andrshown inthe accom,- panying drawings shall beinterpreted as illustrative` and notlimitative;-

We claim:

l. A'flow controlvalve comprising' a hollow valvebody having anoutlet port adjacent its open top end and an nletvportl adjacent its closedbottom end, a hollow sleeve in saidbody havingadiaphragm bottom end portionl con'- tacting the walls of said body and dividing the hollow thereof into; a chamber openingi'nto sai-d inletport' and a chamberl opening into said outlet port; the bore of said sleevebeing enlarged adjacent its' bottom end, said diaphragm portion having bores thereiny openingA into; said sleeve bore enlargement and into said outlet chamber, a hollow* piston movable irl-said inlet chamber andcontact'- ing.` the walls ofl said body tok prevent communication between the hollow of saidfpiston -andsaid' inlet port,a hollow shank integral with said piston and extending into said sleeve bore to seal communication between said sleeve bore enlargement and the upper end of said sleeve bore and to place the hollow of said piston in communication with the upper end of said sleeve bore, said shank being enlarged adjacent its lower end and having a peripheral valve surface formed thereon adapted to seat on the periphery of said sleeve bore at the bottom of said sleeve, a spring bearing on the bottom of said body and on said piston constantly urging said piston upwards to seat said valve surface, a restricted passageway in said shank com* municating the hollow of said shank with said inlet charnber, a cap member closing the top end of said body and sealing the upper end of said sleeve bore from said outlet chamber, said cap having a bore therein in communication with said sleeve bore, the lower end of said cap bore being enlarged, said cap bore having a lateral branch above said enlargement therein, a bleed port in said cap member open-ing into said lateral bore branch, and a valve member in said cap bore movable longitudinally therein, said valve member including an enlarged end portion in said cap bore enlargement, said enlarged vaive end portion having a valve surface formed thereon and adapted to seat on the shoulder in said cap at the top of said bore cap enlargement, and a plug portion adapted to lit snugly in said cap bore between said lateral bore branch and said cap bore enlargement, said plug having a longitudinal groove cut in the surface thereof, said groove increasing in cross-section upwardly of its length.

2. A flow control valve comprising a hollow valve body having an outlet port adjacent its open top end and an inlet port adjacent its closed bottom end, a hollow sleeve in said body having a diaphragm bottom end portion contacting the walls of said body and dividing the hollow thereof into a chamber opening into said inlet port and a chamber opening into said outlet port, the bore of said sleeve being enlarged adjacent its bottom end, said diaphragm portion having bores therein opening into said sleeve bore chamber and into said outlet bore chamber, a hollow piston movable in said inlet chamber and contacting the walls of said body to prevent communication between the hollow of said piston and said inlet port, a hollow shank integral with said piston and extending into said sleeve bore to seal communication between said sleeve bore enlargement and the upper end of said sleeve bore and to place the hollow of said piston in communication with the upper end of said sleeve bore, said shank being enlarged adjacent its lower end and having a peripheral valve surface formed thereon adapted to seat on the periphery of said sleeve bore at the bottom of said sleeve, a spring bearing on the bottom of said body and on said piston constantly urging said piston upwards to seat said valve surface, a restricted passageway in said shank communicating the hollow of said shank with said inlet chamber, a cap member closing the top end of said body and sealing the upper end of said sleeve bore from said outlet chamber, said cap having a bore therein in communication with said sleeve bore, said cap bore being enlarged at its lower end and having a lateral branch above said enlargement, a bleed port in said cap opening into said lateral bore branch, a valve member in said cap bore movable longitudinally therein, said valve member includng an enlarged lower end portion in said cap bore enlargement and provided with a valve surface thereon adapted to seat on the shoulder in said cap at the top end of said cap bore enlargement, and a plug portion adapted to t snugly in said cap bore between said lateral bore branch and said cap bore enlargement, said plug portion having a longitudinal groove cut in the surface thereof whose cross-section increases upwardly of its length, and a top end portion extending beyond said cap through which said valve member may be moved, and spring means bearing on said enlarged lower end of said valve member constantly urging said valve member upwardly to seat said valve surface on said shoulder.

3. A flow control valve comprising a hollow valve body having an outlet port adjacent its open top end Vand an inlet port adjacent its closed bottom end, a hollow sleeve in said body having a diaphragm bottom end portion contacting the walls of said body and dividing the hollow thereof into a chamber opening into said inlet port and a chamber opening into said outlet port, the bore of said sleeve being enlarged adjacent its bottom end, said diaphragm portion having bores therein opening into said sleeve bore enlargement and into said outlet chamber, a hollow piston movable in said inlet chamber and contacting the walls of said body to prevent communication between the hollow -of said piston and said inlet port, a hollow shank integral with said piston and extending into said sleeve bore to seal communication between said ysleeve bore enlargement and the upper end of said sleeve bore and to place the hollow of said piston in communication with the upper end of said sleeve bore, said shank being enlarged adjacent its lower end and having a peripheral valve surface formed thereon adapted to seat on the periphery of said sleeve bore at the bottom of said sleeve, a spring bearing on the bottom of said body and on said piston constantly urging said piston upwards to seat said valve surface, a restricted bore in said shank communicating the hollow of said shank with said inlet chamber, a cap member closing the top end of said body and sealing the upper end of said sleeve bore from `said outlet chamber, said cap having a T-shaped bore therein, the major branch of said T-shaped bore having the lower end thereof enlarged and in communication with said sleeve bore, a bleed port in said cap opening into the minor branch of said cap bore, a pressure equalizing passageway in said cap member placing the top and the bottom end of said major branch in communication, means in said cap sealing the upper end :of said major branch, a valve member longitudinally movable in said major branch, said valve member -including an enlarged lower end portion provided with a valve surface adapted to seat on the shoulder `of said cap at the top end of said major branch enlargement, and a plug portion extending from said enlarged lower end portion adapted to tit snugly within said major branch between said cap shoulder and said minor branch, said plug portion having a longitudinal groove cut in the surface thereof, said groove increasing in cross-section upwardly of said plug portion, said plug portion also having a spaced piston portion fitting snugly in said major branch between said minor branch and the top end of said major branch, and a stem extending from said piston portion upwardly through said major branch 'sealing means to permit external operation of said valve member, the `surface of said piston portion exposed to the pressure conditions at the top of said major bore branch and the surface of said enlarged lower end portion exposed to the pressure conditions in said enlargement of said main bore branch being of such extent and so disposed that the forces tending to move said valve member due to the pressure conditions at the ends of said major bore branch Vare substantially equalized, and spring means engaging said enlarged lower end portion constantly urging said valve member upward.

Wagner Dec. 3, 1912 Gardiner Feb. 21, 1950 

